Way up in the snowy Alps, the border between Switzerland and Italy has shifted due to a melting glacier. It is putting the location of an Italian mountain lodge in dispute. The borderline runs along a drainage divide - the point at which meltwater will run down either side of the mountain towards one country or the other.

But the retreat of the Theodul Glacier means the watershed has crept towards the Rifugio Guide del Cervino, a refuge for visitors near the 3,480-metre Testa Grigia peak. Now it is gradually sweeping underneath the building. Frederic, a 59-year-old tourist, opens the narrow wooden door to enter the refuge's restaurant, the light flooding in from outside.